A form of magnetron such as that disclosed in the U.S. Pat. No. 3,792,306 which issued in the name of Smith et al. on Feb. 12, 1974 has an anode in the form of a circular cylindrical tube with radial vanes extending inwardly therefrom. A magnetron with a similarly formed anode finds extensive use today in microwave ovens. The procedure of the prior art for the manufacture of magnetrons is unduly expensive, particularly in the foregoing situation wherein large numbers of magnetrons are manufactured. The cost is also a problem when such internally vaned tubing is utilized in other situations such as a fluid conductor in a heat exchanger.